Season Two Research Files
Episode Ten
5:00pm-6:00pm
INFRARED IMAGING
Infrared is heat radiation emitted by anything with a temperature -- even objects considered to be very cold. Infrared images project the heat radiated by objects.
The primary source of infrared radiation is heat, or thermal radiation. Heat is the energy that an object has because of the motion of its molecules, which are continuously jiggling and moving around. When energy is added to an object, its molecules move faster, creating more heat. Compared to a warm object, the molecules in a cold object have less molecular motion. Heat is the total energy of molecular motion in a substance. The higher the temperature, the more the atoms and molecules move and the more infrared radiation they produce. Any object having a temperature above absolute zero (-459.67 degrees Fahrenheit or -273.15 degrees Celsius or 0 degrees Kelvin), radiates in the infrared. Absolute zero is the temperature at which all atomic and molecular motion ceases. Even objects that we think of as being very cold, such as an ice cube, emit infrared. When an object is not quite hot enough to radiate visible light, such as a hot piece of charcoal, it will emit most of its energy in the infrared.
Humans, at normal body temperature, radiate most strongly in the infrared at a wavelength of about 10 microns (A micron is the term commonly used in astronomy for a micrometer or one millionth of a meter). In infrared images, the red areas are the warmest, followed by yellow, green and the coolest, blue.
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